This invention relates to a high speed pneumatic actuator, and more particularly relates to an electrohydraulic/pneumatic method of controlling pneumatic servo actuators for use in control applications such as robotics.
Actuators are roughly divided into three classes: hydraulic, pneumatic, and electromechanical.
Hydraulic actuators are preferably used in applications requiring precise positioning because hydraulics exhibit absolute breaking force properties but tend to be prohibitively expensive--typically costing $20,000 per axis of movement. Furthermore, hydraulic actuators pose leakage and environmental problems making their use either impractical or impossible in certain applications such as food handling.
Electromechanical actuators, such as those using ball gears, have the benefit of extremely precise positioning. A drawback, however, is that the mechanical components driving the actuator have a short life span especially when high speeds are involved.
The present pneumatic servo actuators while offering high speed actuation are very difficult to control with precision, primarily due to the compressibility of air which causes springiness of movement. Robotics using pneumatic actuators tend to be limited to single destination machines such as pick and place devices. The present invention eliminates this problem by providing an incompressible braking medium throughout the actuator's operating range so as to eliminate the springiness inherent in a compressible medium. As a result, a robotics device can be precisely controlled over a potentially infinite range of positions.
Accordingly it is an object of the present invention to provide a high speed pneumatic servo actuator using a novel hydraulic damper that allows accurate positioning of the actuator without the springiness of movement resulting from gas compressibility.
It is also an object of the present invention to provide closed loop electronic control of the actuator from a microprocessor.
Additional objectives and advantages of the present invention will be made apparent in the following description with reference to the accompanying drawings.